One of the purposes of researchers in the scientific discipline of chemistry education is to popularise research findings among students, future chemistry teachers. By informing teachers of chemistry education at the university level and teachers of chemistry at the primary and secondary level about the results of the study and transferring the findings into the educational process, we will contribute to a more successful education in the field of chemistry. Researchers in the field of chemistry education devote much of their research interests to investigating the understanding of the triple nature of chemical concepts in connection with visualisation and other measures that further influence the acquisition of qualitative knowledge of chemical content without developing misconceptions. Based on the relevant theoretical starting points, a research problem was formulated to address the conceptual understanding of chemical reactions at three levels of representation of chemical concepts. The main purpose of the study was to determine what strategies are used by students of chemistry in the Two-Subject Teacher study programme to solve contextual problems involving chemical reactions and how students in different years of study differ in these problem-solving strategies. Due to the complexity of the concept, the strategy for solving a chemical problem was defined as the use of the expert or non-expert path of attentional fixation that focuses on areas of interest in solving a chemical problem. The study was also conducted to examine how prior chemical knowledge, visualisation, intellectual abilities, and intrinsic motivation influence the prior knowledge and the use of the expert path of fixations when solving a chemical problem. Based on a qualitative analysis of audio recordings combined with the eye-tracker data, the most common misconceptions and incomplete understandings of selected chemical concepts of content about redox reactions were identified. Semi-structured interviews were also performed to identify the possible causes of errors in solving three chemical problems. The eye movement tracking technique was used in the empirical part of the study to triangulate the data, thus contributing to a more objective and reliable interpretation of the results. Fifty-five students of the Two-Subject Teacher study programme majoring in chemistry participated in the study. They took a pre-knowledge test, a series of other tests, and completed a questionnaire. The tests and the questionnaire showed satisfactory measurement characteristics in the included sample.
When solving chemical problems, it was found that the intrinsic motivation for problem-solving was increased by the introductory context, and that all three chemical problems were well known and interesting to the students and posed in the increasing order of difficulty. In predicting the total score in solving chemical problems with different predictors, statistical significance was achieved only by using the expert or non-expert fixation path, while students' definition of difficulty or interestingness did not achieve statistical significance. Students were found to be less successful at solving chemical problems due in part to their lesser ability to integrate more information at the same time, and therefore having more complex, poorer or even incorrect solution approaches (using the non-expert fixation path). Students with poorer prior chemical knowledge, intellectual and visual abilities, solved a more complex chemical problem at a macroscopic rather than a symbolic level. At the same time, more abstract sub-microscopic levels of representation were mostly not used in the solution. It seems that in most cases, the use of the non-expert fixation path, regardless of year of study or prior chemical knowledge, also led to the wrong solution. From the images of the paths and the images of the fixation densities of focused attention when solving chemical problems in student groups of different year levels, it can be generally concluded that the 1st year students and the students who solved the chemical problem using the non-expert fixation path read the instructions several times. The number of connections between different areas of interest of the chemical problem that were rated as difficult or very difficult was higher among students with good chemistry knowledge, who solved the problem using the expert fixation path. Lower-year students, students with poor prior chemical knowledge, and students who solved the chemical problems using the non-expert fixation path were more likely to link the macroscopic and symbolic levels, while the sub-microscopic level was repeatedly omitted. Students, regardless of year of study, who solved chemical problems using the expert fixation path paid greater attention to the symbolic level than students who solved the chemical problem through the non-expert fixation path. In addition to using the expert fixation path, attention to the symbolic level was significantly influenced by appropriate prior chemical knowledge, high levels of formal thinking, and appropriate working memory capacity. Students with low prior chemical knowledge mostly used the same solution algorithm (using the non-expert fixation path) when solving the problem, which was simple enough for them to understand it relatively well. Students with good knowledge of chemistry tried to convert or rewrite individual points of the chemical problem into a simple task, which also led them to an easier solution path. The students who solved the chemical problem using the expert fixation path found it easier and faster to find a strategy to solve the chemical problem, which usually led them to the correct solution. In predicting the student's placement into the higher or lower group according to their performance in redox reactions, as well as in predicting the use of the expert fixation path with the predictors of intrinsic motivation, visualisation skills, intellectual ability, and prior chemical knowledge, it was the intellectual ability (logical thinking and working memory capacity) and prior chemical knowledge that reached the level of statistical significance. Statistical significance was not achieved in intrinsic motivation for learning chemistry at three levels of presentation of chemical concepts and in visualisation skills. The fact that visualisation skills did not emerge as an important predictor of chemical problem solving may be explained in part by the fact that the chemical problems in this study required the integration of at least eight different areas of interest at all three levels of chemical concept representation. It is also possible that visualisation skills fall only under a set of general cognitive skills. While they play a key role for understanding the abstract sub-microscopic level of representation, they do not have a major impact on solving complex contextual chemical problems at three levels of representation if examined as an independent factor. However, better performance in redox reactions or the use of the expert path of fixation in solving such chemical problems are attained by those students who are sufficiently internally motivated to solve such chemical problems. When teaching abstract chemical content, it is crucial that the teacher supports the student at three levels of representation of the chemical concept to achieve better understanding when solving chemical problems. They must guide the student to the correct solution path by explaining and showing them the expert solution path. The teacher should help the student to develop problem-solving skills and competencies and encourage learning with understanding. In this way, the individual develops long-term and high-quality chemical knowledge.
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